Method of manufacturing an array substrate for use in a reflective liquid crystal display device

ABSTRACT

The present invention discloses a method of manufacturing an array substrate for use in a reflective liquid crystal display device, including: providing a thin film transistor array substrate; depositing a metal layer on the substrate using a shadow mask having a plurality of holes; and patterning the metal layer into a reflective electrode for connecting to the thin film transistor.

CROSS REFERENCE

[0001] This application claims the benefit of Korean Patent ApplicationNo. 1999-63249, filed on Dec. 28, 1999, under 35 U.S.C. § 119, theentirety of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the invention

[0003] The present invention relates to a liquid crystal display (LCD)device, and more particularly to a method of manufacturing an arraysubstrate for use in a reflective LCD device.

[0004] 2. Description of Related Art

[0005] Liquid crystal display (LCD) devices are in wide use as displaydevices capable of being reduced in weight, size and thickness. Ingeneral, the LCD device includes upper and lower substrates with aliquid crystal layer interposed therebetween. The upper substrateincludes a common electrode and a color filter, and the lower substrateincludes a pixel electrode and TFTs. An upper polarizer is arranged on afront surface of the upper substrate, and a lower polarizer is arrangedon a bottom surface of the lower substrate. A back light device isarranged under the lower substrate as a light source.

[0006] The LCD device is divided into a transmissive LCD device and areflective LCD device. The typical transmissive LCD device displaysimages using light from the back light device. However, the transmissiveLCD device is a non-effective light converter that merely transmitsabout 3% to about 8% of light from the back light device. In otherwords, as shown in FIG. 1, observer gets to see about 7% of light fromthe back light device. Therefore, the transmissive LCD device requires aback light device having a high brightness, leading to a high powerconsumption.

[0007] In order to achieve the back light device having a highbrightness, a sufficient power must be supplied to the back lightdevice, thereby increasing a battery weight. However, even such a backlight device can not be used for a long time.

[0008] To overcome the problems described above, the reflective LCDdevice has been introduced. Since the reflective LCD device is drivenusing ambient light, a power consumption becomes lowered, whereby it ispossible to use for a long time and it is easy to carry due to its lightweight.

[0009]FIG. 2 is a plan view illustrating a lower array substrate of aconventional reflective LCD device. As shown in FIG. 2, data lines 2 and4 are arranged in a longitudinal direction, and gate lines are arrangedin a transverse direction perpendicular to the data lines 2 and 4. Areflective electrode 10 is arranged on a region defined by the gate anddata lines. TFTs are arranged at a cross point of the gate and datalines. Each of the TFTs includes a gate electrode 18, a source electrode12 and a drain electrode 14. The gate electrode 18 extends from the gateline 8, and the source electrode 12 extends from the data line 12. Thedrain electrode 14 is spaced apart from the source electrode 12 andcontact the reflective electrode 10 through a contact hole 16.

[0010]FIG. 3 is a cross sectional view taken along line III-III of FIG.2. As shown in FIG. 2, the gate electrode 18 is formed on a substrate 1,and a gate insulating layer 20 is formed on the gate electrode 18 and anexposed surface of the substrate 1. A semiconductor layer 22 is formedon the gate insulating layer 20. The source and drain electrode 12 and14 overlaps both end portions of the semiconductor layer 22. Apassivation film 24 is formed over the whole surface of the substrate 1while covering the source and drain electrodes 12 and 14. Thepassivation film 24 has the contact hole 16 on a portion of the drainelectrode 14. The reflective electrode 10 is formed on the passivationfilm and contacts the drain electrode 14 through the contact hole 16.The reflective electrode is made of a material having a goodreflectance.

[0011] As described above, since the reflective LCD device uses ambientlight other than an internal light source such as a back light device,it can be used for a long time. In other words, the reflective LCDdevice is driven using light reflected from the reflective electrode 10.

[0012] However, as shown in FIG. 3, the reflective electrode 10 has aflat structure, and thus a mirror effect may occur when an observerviews images displayed by the reflective 10. In other words, a face ofan observer may be reflected by the flat reflective electrode 10 due tothe flat reflective electrode 10. Further, since not a back light butambient light is used, a brightness is relatively low.

[0013] In order to overcome the problems described above, as shown inFIG. 4, a reflective electrode having concave or convex portions 30 hasbeen introduced. The reflective electrode 10 having the concave orconvex portions 30, as shown in FIG. 5, causes diffused reflection,thereby reducing a mirror effect.. In addition, since a reflection areaof the reflective electrode 10 increases due to a thickness of thereflective electrode 10, a brightness increases. Typically, in order toform the concave or convex portions 30 of the reflective electrode 10,the passivation film 24 and the insulating layer 20 at a pixel portionare etched through at least twice mask processes. Therefore, amanufacturing process increases in number, and a manufacturing yield islowered.

[0014] For the foregoing reasons, there is a need for a reflectiveliquid crystal display device having a high brightness and a highmanufacturing yield that is manufactured by a simple process.

SUMMARY OF THE INVENTION

[0015] To overcome the problems described above, preferred embodimentsof the present invention provide a reflective liquid crystal displaydevice having a high brightness and a high manufacturing yield that ismanufactured by a simple process.

[0016] In order to achieve the above object, the preferred embodimentsof the present invention provide a method of manufacturing an arraysubstrate for use in a reflective liquid crystal display device,including: providing a thin film transistor array substrate; depositinga metal layer on the substrate using a shadow mask having a plurality ofholes; and patterning the metal layer into a reflective electrode forconnecting to the thin film transistor.

[0017] The present invention further provides a method of manufacturingan array substrate for use in a reflective liquid crystal displaydevice, including: providing an deposition equipment having a sputteringtarget, a thin film transistor array substrate, and a mask, the maskhaving a plurality of holes and located between the sputtering targetand the substrate; depositing a metal layer on the substrate by allowingmetal particles generated from the target to pass through the holes; andpatterning the metal layer into a reflective electrode.

[0018] The holes of the mask have one of a trapezoid, a circular and arectangular cross section.

[0019] Using a mask used to form a reflective electrode of a reflectiveLCD device according to the preferred embodiment of the presentinvention, since additional process to form the concave or convexportion is not required, a manufacturing process is simplified, therebyincreasing a manufacturing yield. In addition, since the reflectiveelectrode has concave or convex portions, a brightness can increase.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a more complete understanding of the present invention andthe advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying drawings, inwhich like reference numerals denote like parts, and in which:

[0021]FIG. 1 is a graph illustrating transmittance after light passesthrough each layer of a conventional liquid crystal display device;

[0022]FIG. 2 is a plan view illustrating a lower array substrate of aconventional reflective LCD device;

[0023]FIG. 3 is a cross sectional view taken along line III-III of FIG.2;

[0024]FIG. 4 is a cross sectional view illustrating a modifiedreflective electrode of the conventional reflective LCD device;

[0025]FIG. 5 is an enlarged view illustrating a portion A of FIG. 4;

[0026]FIG. 6 is a plan view illustrating a mask used to form areflective electrode of a reflective liquid crystal display (LCD) deviceaccording to a preferred embodiment of the present invention;

[0027]FIG. 7 is a cross-sectional view taken along line VII-VII of FIG.6; and

[0028]FIG. 8 is a cross-sectional view illustrating the reflectiveelectrode formed by the deposition method according to the preferredembodiment of the present invention

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0029] Reference will now be made in detail to a preferred embodiment ofthe present invention, example of which is illustrated in theaccompanying drawings.

[0030]FIG. 6 is a plan view illustrating a mask used to form areflective electrode of a reflective liquid crystal display (LCD) deviceaccording to the preferred embodiment of the present invention. As shownin FIG. 6, the mask 200 includes a plurality of holes 210. The holes 210is placed at an intermediate location between a test piece (i.e., a thinfilm transistor array substrate) and a sputtering target in an equipmentused to deposit a metal thin film, for example, a sputter. Metalparticles spattered from the sputtering target passes through the holes210 to be deposited on the test piece. The mask 200 is referred to as ashadow mask. Preferably, the holes 210 have a trapezoid cross section(see FIG. 7). The holes 210 may have a circular and a rectangular crosssection, and therefore a shape of the holes 210 is limited to thepresent invention.

[0031] In order to form the reflective electrode having concave orconvex portions, in the preferred embodiment of the present invention,the insulating layer and the passivation film are not etched. When ametal layer for the reflective electrode is formed, the concave orconvex portions are formed at the same time. In other words, using theshadow mask 200, the reflective electrode having the concave or convexportions can be formed.

[0032]FIG. 7 is a cross-sectional view taken along line VII-VII of FIG.6. A method of forming the reflective electrode of the reflective LCDdevice is explained below in detail with reference to FIG. 7. As shownin FIG. 7, first a substrate 1 on which the reflective electrode is formis placed in a deposition equipment for a metal thin film such as asputter and a evaporator. A target 300 of a thin film is placed over thesubstrate 1, and the mask 200 is placed between the substrate 1 and thetarget 300. Then, using the shadow mask 200 having a plurality of theholes 210, a metal thin film is deposited on the substrate 1. At thistime, the metal particles generated from the target 300 pass through theholes 210. As a time of depositing a metal thin film becomes lengthy,the holes 210 are clogged by the metal particles 230, and an amount ofthe metal particles that pass through the holes 210 is graduallydecreased. As a result, a metal layer that is deposited on the substrate1, i.e., the reflective electrode 240 gets to have the concave or convexportions 250.

[0033] Using the method of depositing a metal thin film described above,the reflective electrode having the concave or convex portions can beformed without any additional processes.

[0034]FIG. 8 is a cross-sectional view illustrating the reflectiveelectrode formed by the deposition method according to the preferredembodiment of the present invention. As shown in FIG. 8, the concave orconvex portions 250 have a triangular cross section. Therefore, areflection index is improved, leading to a high brightness.

[0035] As described herein before, using a mask used to form areflective electrode of a reflective LCD device according to thepreferred embodiment of the present invention, since additional processto form the concave or convex portion is not required, a manufacturingprocess is simplified, thereby increasing a manufacturing yield. Inaddition, since the reflective electrode has concave or convex portions,a brightness can increase.

[0036] While the invention has been particularly shown and describedwith reference to first preferred embodiments thereof, it will beunderstood by those skilled in the art that the foregoing and otherchanges in form and details may be made therein without departing fromthe spirit and scope of the invention.

What is claimed is:
 1. A method of manufacturing an array substrate foruse in a reflective liquid crystal display device, comprising: providinga thin film transistor array substrate; depositing a metal layer on thesubstrate using a shadow mask having a plurality of holes; andpatterning the metal layer into a reflective electrode for connecting tothe thin film transistor.
 2. The method of claim 1 , wherein the holesof the shadow mask have one of a trapezoid, a circular and a rectangularcross section.
 3. A method of manufacturing an array substrate for usein a reflective liquid crystal display device, comprising: providing andeposition equipment having a sputtering target, a thin film transistorarray substrate, and a mask, the mask having a plurality of holes andlocated between the sputtering target and the substrate; depositing ametal layer on the substrate by allowing metal particles generated fromthe target to pass through the holes; and patterning the metal layerinto a reflective electrode.
 4. The method of claim 3 , wherein theholes of the mask have one of a trapezoid, a circular and a rectangularcross section.